1. Field of the Invention
The present invention relates generally to a system and a method for displaying panoramic and horizontally immersive images.
2. Brief Description of the Prior Art
A first class of prior art panoramic or immersive image display systems use a window corresponding more or less to the field of vision of a spectator. This window can be displaced by the spectator to show different portions of 360° panorama or of a sphere or a segment of a sphere around the point of view. The window is, for example, the fixed screen of a computer; a screen or projection moving around viewers and displaced either manually or automatically by, for example, head or body tracking; or a headset with an eye piece and a device for displacing the field of vision in relation to movement of the spectator's head.
The prior art systems of the first class present the drawback, for the head mounted displays versions, of isolating the spectator and require for each spectator complex adjustment and handling. The prior art systems of the first class also present the drawback, for the screens versions, to produce no definite feeling of immersion (i.e., the spectator is not at least partially surrounded by images) and an undesirable phenomenon known as tunnel vision.
A second class of prior art systems uses the juxtaposition of several images to form a full “composite” panoramic image. This technique creates a horizontally immersive space that can be shared simultaneously by many individuals that are free to look around. To create the full panoramic space, either projection (front or rear projection on a cylindrical or spherical screen) or juxtaposition of video monitors (video wall) can be used. Panoramic projection requires a number of projectors and image sources to cover, by front or rear screen projection, segments of a 360° cylindrical screen or of a sphere or frustum of a sphere.
Due to the high cost and high complexity connected to the presentation of panoramic programs using a plurality of projectors or monitors, the prior art systems of the second class are generally custom designed and dedicated to specific applications with the result that such systems are rare, ephemeral, and that no significant sharable repertoire of content exists for them.
A third class of prior art systems uses hemispheric projection to cover more or less a full half sphere using a single image source and projection apparatus. These systems generally used in planetariums and other types of hemispheric theatres, such as those developed by IMAX Corporation and Elumens Corporation among others, are designed to cover the entire field of vision of a sitting or standing audience looking generally in the same direction.
U.S. Pat. No. 5,762,413, issued to Colucci et al. on Jun. 9, 1998, discloses a tiltable hemispheric optical projection system. This projection system comprises a downwardly flaring hemisphere having an inner surface that serves as a hemispheric screen. Projection optics are upstanding from the ground to the center of the hemisphere, and project images on given areas of the hemispheric screen. People are positioned on the ground in the hemisphere so as to be in position to observe the images projected on the hemispheric screen. The projection optics that project the images on the hemispheric screen are positioned in the center of the hemisphere and are thus at a generally constant radius from the hemispheric screen, so as to produce little distortion when projecting images thereon. The projection optics are pivotally mounted on a base so as to be oriented to project the images on various portions of the hemispheric screen.
The prior art systems of the third class do not have the viewers surrounded by the projection area, and thus always come short of full horizontal 360° immersivity. Because of this, the prior art systems of the third class can be compared with the prior art systems of the afore-mentioned first class where full horizontal panoramic imaging can only be achieved by moving the hemispheric projection apparatus about the entire image, with the drawback that the audience is not free to look around as they can in fully immersive panoramas.
A fourth class of prior art systems also uses hemispheric projection to cover at least a full half of a hemispheric screen, but have the projectors positioned such that a spectator in the hemisphere is surrounded by images.
U.S. Pat. No. 6,327,020, issued on Dec. 4, 2001 to Iwata, discloses a full-surround spherical screen projection system. The full-surround spherical screen projection system comprises a sphere provided with an inner spherical screen for the projection of 360° peripheral images by way of a single projector. The projector is preferably placed vertically in an upper portion of the sphere above a spectator in the sphere, and projects images through a hole in a first convex annular mirror. The projected image is first reflected by a second mirror within the sphere towards the first convex annular mirror, which reflects the image towards the spherical screen. The spectator is preferably positioned so as to have his head in the center of the sphere. The positioning of the first and second mirrors in the sphere requires that the image projected by the projector be distorted in order to get a distortion-free image on the screen. Accordingly, a recording apparatus is required to enable capturing highly distorted images that will correspond to the positioning of the mirrors in the sphere so as to produce distortion-free images. The severe alteration of the images to produce distortion-free images from such an eccentric position involves a complex solution and one that will not guarantee adequate image quality especially in the bottom half of the sphere. Another drawback is that it will be practically impossible to guarantee an even image brightness on the surface of the sphere since the projection distance varies considerably between the top and bottom of the sphere. Furthermore, mirrors are not a cost-effective solution and must be positioned with precision, and this is costly labour-wise.